AN ANTENNA DEVICE FOR PORTABLE EQUIPMENT

Description

[0001] The invention relates to an antenna device for portable equipment, particularly for hand portable telephones.

[0002] Antennas for mobile telephones may be divided into two main groups, quarter-wave and half-wave antennas, although types somewhere between and outside these may occur.

[0003] Characteristics of a quarter-wave antenna are:

• the length of its actively radiating portion is one quarter of a wavelength (portion length approximately 8 cm at 900 MHz),
• its feeding connection impedance is low, which allows its direct connection to the 50 Ohm of the telephone, without impedance transformation,
• due to its short length a 900 MHz telephone user will not consider it disturbing,
• it is dependent on a ground plane for its function.

[0004] Characteristics of a half-wave length antenna are:

• the length of its actively radiating portion is one half of a wavelength (portion length approximately 16 cm at 900 MHz),
• its feeding connection impedance is high, which requires impedance transformation to the 50 Ohm of the telephone,
• it is unsuitable to small telephone due to its total length of 18 - 20 cm including a connector,
• it is independent of a ground plane for its function.

[0005] In the specification and claims below the terms half-wave antenna and quarter-wave antenna refer to antennas having substantially the above characteristics, respectively.

[0006] One disadvantage in using the quarter-wave antenna, which is dependent on a ground plane, is that the ground plane offered in hand portable telephone is in most cases smaller than one wavelength in a radius from the feeding point of the antenna. As a result, the ground plane becomes resonant and, consequently, it must be tuned to the antenna for optimal performance. Moreover, the ground plane characteristics change (and so the antenna performance) depending on whether the telephone is placed freely, whether the telephone (the ground plane) is held with the hand, whether the user is perspiring, whether the telephone is moved to the ear etc.

[0007] Another disadvantage in using a quarter-wave antenna for a hand portable telephone is, in fact, its small length. This causes the antenna, while in call position, to be strongly screened in a substantial angle sector by the head of the user.

[0008] In spite of the above mentioned disadvantages, the most common antenna for hand portable telephones is a quarter-wave length antenna, since a small antenna is needed to regard the telephone as hand portable or a pocket telephone. Recently, a type of hand portable telephone has appeared, which are provided with extendable half-wave antennas. This is an acceptable solution from the handling point of view, since the antenna requires a small space in the retracted position. The problem in this case is that the antenna function is so poor in the retracted position that it might be difficult to receive an incoming call.

[0009] US-A- 4 868 576 discloses an antenna for a portable cellular telephone , which includes a quarter-wavelength ground radiator and a helical coil capacitively coupled to an extendable half-wavelength radiator. The extendable half-wavelength radiator includes a metallic coil molded in plastic. The ground radiator includes a serpentined transmission line on a flexible circuit board.

[0010] Another known type of mobile telephones employs in combination a considerably more compact helical antenna of quarter-wave type as an antenna for receiving an incoming call, and a half-wave antenna which is extended in call position. However, this arrangement is unsatisfactory due to the ground plane dependence of the helical antenna and the switching between the helical antenna and the half-wave antenna being complicated, since only one antenna at the time may connected. Also, a helical antenna has a lower degree of efficiency than e.g. a rod antenna.

[0011] All the above mentioned disadvantages are overcome by an antenna device according to the present invention.

[0012] This new antenna device for portable equipment uses in combination a helical antenna of half-wave length type arranged outside of a main body of said portable equipment, an extendable half-wave antenna, and an impedance transformer. Therefore, no ground plane is required for the antenna function. Further, due to the sufficient length of the half-wave length antenna, the problem of the user's head screening the antenna is substantially reduced. Yet further, a very simple switching may be performed, since the helical antenna and half-wave length antenna may utilize the same impedance transformer. The half-wave length antenna, when in use, may even be connected parallel to the helical antenna due to impedance differences. According to the invention this possibility is utilized and, therefore, only a very simple switching device is required. The switching device may be operated by extending and retracting of the antenna.

[0013] In the retracted position (see Fig. 3a) the half-wave length antenna is neither galvanically nor capacitively coupled to the impedance transformer. In this position the antenna function consists of only the helical antenna, which is constantly coupled to the impedance transformer. In the retracted position at possible coupling the lower end is transformed with high impedance to the upper end, which minimized the influence.

[0014] In the extended position the helical antenna and the half-wave length antenna are connected in parallel to the impedance transformer. Since the impedance of the half-wave length antenna is small compared to the impedance of the helical antenna the antenna function in this position is substantially the same as for a half-wave antenna.

[0015] Thus, with the described device one meets the demands of antenna size in order to consider the telephone as hand portable, antenna performance in call position, and the telephone accessibility for incoming calls, when the half-wave antenna is in its retracted position.

[0016] The invention will be described below in the form of two embodiments with reference to the attached drawings, wherein:
Fig. 1 is a view of an embodiment of the antenna device according to the invention.
Fig. 2 shows with separated components parts of the antenna device of Fig. 1.
Fig. 3a shows details of for instance a switching device of the antenna device of Fig. 1.
Fig. 3b, 3c are two views of details of for instance an impedance transformer of the antenna device of Fig. 1.

[0017] The antenna device according to a preferred embodiment, shown in Figs. 1, 2, 3a, and 3b, consists of three main components.

[0018] First a half-wave antenna 1 (rod antenna), the lower end 2 of which is bare to facilitate the galvanic coupling, while it is otherwise provided with an insulating case 3, and the upper end of which is attached to an upper part 4 made of insulating material. Together the half-wave antenna 1 and the upper part 4 form an antenna rod, which is preferably provided with a knob 5 in its upper insulating end.

[0019] Secondly, a helical antenna 6 of half-wave length type, which is moulded into a casing 7 made of protective, insulating material, which in its lower end has a fastened sleeve 12 made of conducting material. The sleeve 12 is mechanically and galvanically coupled to the lower of the helical antenna 6 and contains an elastic contact part 13. The antenna rod 1 is movably arranged through the helical antenna 6, the casing 7, the sleeve 12 and the contact part 13.

[0020] The above mentioned parts are substantially symmetrically arranged with regard to the central length axis of the antenna rod.

[0021] Thirdly, an impedance transformer 8, which, for example, consists of an inductive component 9 mounted on a circuit board 11, the capacitance of which is tuned to the environment. The impedance transformer is provided with a coaxial cable 14 connected to the transceiver part of the telephone, and with a galvanic coupling to the sleeve 12 through a connection loop 10, the sleeve 12 is also a connection device to the hand portable telephone 15 for the antenna device. Preferably, a protective insulating tube 16 is attached on the underneath side of the sleeve 12, into which tube 16 the antenna rod travels when retracted through the sleeve 12.

[0022] In mobile telephones transmitting and receiving takes place as well when no call is going on. In this case the antenna rod is completely retracted, so that its upper, non-conductive part 4 is located inside the helical antenna. When so the half-wave antenna is galvanically and substantially capacitively separated from the helical antenna 6, the latter effecting the total antenna function.

[0023] During a call, or when otherwise required with regard to antenna performance, the half-wave antenna is extended, its lower part 2 being galvanically coupled, via the contact part 13, in parallel with the helical antenna 6, to the impedance transformer 8. Since the impedance of the half-wave antenna 1 is low compared to the impedance of the helical antenna 6, the antenna function in this case is substantially the same as of a half-wave antenna alone.

[0024] Thus, the coupling and decoupling of the half-wave antenna 1 is effected by extending and retracting of the antenna rod 1, respectively. The extension of the antenna rod is limeted by lower part 2 of the half-wave antenna being stopped by the contact part 13 and the sleeve 13. The contact part 13 also serves as a mechanical locking mechanism of the antenna rod in its extended position, while its retracting movement is limited by e.g. the knob 5 or a bottom of the insulated tube 16.

Claims

1. An antenna device of a portable equipment for transmitting and/or receiving of radio signals, said antenna device comprising a helical antenna (6) sustantially having the characteristics of a half-wave antenna, a half-wave antenna (1), and an impedance transformer (8), said helical antenna (6), said half-wave antenna (1), and said impedance transformer (8) being intercouplable in at least two different combinations constituting different working antenna functions,
characterized in that, in order to form two different working antenna functions, either said helical antenna (6) alone is conductively coupled to said impedance transformer (8) or said helical antenna (6) and said half-wave antenna (1) are conductively coupled in parallel to said impedance transformer (8).

2. An antenna device as claimed in claim 1,
characterized in that said antenna device is provided with a switching device (2, 12, 13), which to said impedance transformer (8) either couples conductively said half-wave antenna (1) in parallel with said helical antenna (6) or decouples said half-wave antenna (1).

3. An antenna device as claimed in any one of claims 1-2,
characterized in that the characteristics of either the helical antenna (6) or the half-wave antenna (1) are utilized mainly, at different demands for antenna performance.

4. An antenna device as claimed in claim 2 or 3,
characterized in that said half-wave antenna (1) is extendable and retractable.

5. An antenna device as claimed in claim 4,
characterized in that said half-wave antenna (1) is telescopically extendable and retractable.

6. An antenna device as claimed in claim 2 or 4,
characterized in that said half-wave antenna (1) is provided with a switching device (2, 12, 13) operative to couple said half-wave antenna (1) when being extended and to decouple said half-wave antenna (1) when being retracted.

7. An antenna device as claimed in claim 6,
characterized in that said swithing device (2, 12, 13) also serves as a mechanical locking mechanism of the half-wave antenna (1) in its extended position.

8. An antenna device as claimed in claim 6 or 7,
characterized in that said swithing device consists of a lower part (2) of said half-wave antenna, a sleeve (12) coupled to said helical antenna (6) and to said impedance transformer (8), and a contact part (13) interconnecting said lower part (2) and said sleeve (12).

Ansprüche

1. Antennenvorrichtung einer tragbaren Einrichtung zum Senden und/oder Empfangen von Funksignalen, wobei die Antennenvorrichtung eine Wendelantenne (6) mit weitgehend den Eigenschaften einer Halbwellen-Antenne, eine Halbwellen-Antenne (1) und einen Impedanzwandler (8) aufweist, wobei die Wendelantenne (6), die Halbwellen-Antenne (1) und der Impedanzwandler (8) in wenigstens zwei verschiedenen Kombinationen, die verschiedene Antennenbetriebsfunktionen ergeben, miteinander verbindbar sind, dadurch gekennzeichnet, daß zur Erzielung zweier verschiedener Antennenbetriebsfunktionen entweder die Wendelantenne (6) allein mit dem Impedanzwandler (8) leitend verbunden ist oder die Wendelantenne (6) und die Halbwellen-Antenne (1) parallel zueinander leitend mit dem Impedanzwandler (8) verbunden sind.

2. Antennenvorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß die Antennenvorrichtung mit einer Umschaltvorrichtung (2, 12, 13) versehen ist, die den Impedanzwandler (8) entweder leitend mit der Halbwellen-Antenne (1) parallel zur Wendelantenne (6) verbindet oder die Halbwellen-Antenne (1) abschaltet.

3. Antennenvorrichtung nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Eigenschaften entweder der Wendelantenne (6) oder der Halbwellen-Antenne (1) hauptsächlich bei verschiedenen Anforderungen an die Antennenleistung ausgenutzt werden.

4. Antennenvorrichtung nach Anspruch 2 oder 3, dadurch gekennzeichnet, daß die Halbwellen-Antenne (1) ausziehbar und einschiebbar ist.

5. Antennenvorrichtung nach Anspruch 4, dadurch gekennzeichnet, daß die Halbwellen-Antenne (1) teleskopisch ausziehbar und einschiebbar ist.

6. Antennenvorrichtung nach Anspruch 2 oder 4, dadurch gekennzeichnet, daß die Halbwellen-Antenne (1) mit einer Umschaltvorrichtung (2, 12, 13) versehen ist, die derart betätigbar ist, daß sie die Halbwellen-Antenne (1) anschaltet, wenn sie ausgezogen wird, und abschaltet, wenn sie eingeschoben wird.

7. Antennenvorrichtung nach Anspruch 6, dadurch gekennzeichnet, daß die Umschaltvorrichtung (2, 12, 13) auch als mechanische Verriegelungseinrichtung für die Halbwellen-Antenne (1) in ihrem ausgezogenen Zustand dient.

8. Antennenvorrichtung nach Anspruch 6 oder 7, dadurch gekennzeichnet, daß die Umschaltvorrichtung aus einem unteren Teil (2) der Halbwellen-Antenne, einer mit der Wendelantenne (6) und dem Impedanzwandler (8) verbundenen Hülse (12) und einem Kontaktteil (13) besteht, der den unteren Teil (2) und die Hülse (12) miteinander verbindet.

Revendications

1. Dispositif d'antenne d'un équipement portable pour émettre et/ou recevoir de signaux radio, ledit dispositif d'antenne comprenant une antenne hélicoïdale (6) qui a sensiblement les caractéristiques d'une antenne demi-onde, une antenne demi-onde (1) et un transformateur d'impédance (8) ladite antenne hélicoïdale (6), ladite antenne demi-onde (1) et ledit transformateur d'impédance (8) pouvant être couplés mutuellement dans au moins deux combinaisons différentes constituant des fonctions d'antenne opérant différemment,
caractérisé en ce que, afin de former deux fonctions d'antenne travaillant différemment, ladite antenne hélicoïdale (6) seule est couplée conductivement audit transformateur d'impédance (8) ou bien ladite antenne hélicoïdale (6) et ladite antenne demi-onde (1) sont couplées conductivement en parallèle audit transformateur d'impédance (8).

2. Dispositif d'antenne suivant la revendication 1, caractérisé en ce que ledit dispositif d'antenne comprend un dispositif de commutation (2,12, 13) qui connecte conductivement audit transformateur d'impédance (8) ladite antenne demi-onde (1) en parallèle avec ladite antenne hélicoïdale (6), ou déconnecte ladite antenne demi-onde (1).

3. Dispositif d'antenne suivant une quelconque des revendications 1 et 2, caractérisé en ce que les caractéristiques de l'antenne hélicoïdale (6) ou de l'antenne demi-onde (1) sont utilisées principalement, à différentes demandes de performance d'antenne.

4. Dispositif d'antenne suivant la revendication 2 ou 3, caractérisé en ce que ladite antenne demi-onde (1) est extensible et rétractable.

5. Dispositif d'antenne suivant la revendication 4, caractérisé en ce que ladite antenne demi-onde (1) est extensible et rétractable télescopiquement.

6. Dispositif d'antenne suivant la revendication 2 ou 4, caractérisé en ce que ladite antenne demi-onde (1) est pourvue d'un dispositif de commutation (2, 12,13) qui agit pour coupler ladite antenne demi-onde (1) lorsqu'elle est en extension et pour découpler ladite antenne demi-onde (1) lorsqu'elle est rétractée.

7. Dispositif d'antenne suivant la revendication 6, caractérisé en ce que ledit dispositif de commutation (2,12,13) sert également de mécanisme de blocage mécanique de l'antenne demi-onde (1) dans sa position d'extension.

8. Dispositif d'antenne suivant la revendication 6 ou 7, caractérisé en ce que ledit dispositif de commutation est constitué d'une partie inférieure (2) de la dite antenne demi-onde, d'un manchon (12) couplé à ladite antenne hélicoïdale (6) et audit transformateur d'impédance (8) et d'un élément de contact (13) interconnectant ladite partie inférieure (2) et ledit manchon (12).

Drawing